This invention relates to a digital data recording and reproducing apparatus such as for example a digital video tape recorder (hereinafter simply referred to as a digital VTR) which digitizes a video signal to record and reproduce a digital signal and more particularly, to a digital data recording and reproducing apparatus capable of recording and reproducing even a high-definition image of a large sampling image matrix size defined by a great number of scanning lines.
In recent years, advancement in digital integrated circuits has promoted development of digital VTR's which digitize a television video signal to ensure recording and reproduction of high image quality. In the digital VTR, an input video signal received from an external image apparatus is digitized by means of an A/D converter, digital data is recorded on or reproduced from a magnetic recording medium such as a magnetic tape of a recording and reproducing unit of the digital VTR, and the digital data read out of the recording and reproducing unit is converted by a D/A converter into an output video signal. The digital VTR is operative to record and reproduce image frames pursuant to the NTSC system which is the existing standard television system, that is, 30 image frames/second defined by 525 horizontal scanning lines.
Recently, however, an image apparatus for imaging and displaying a high-definition image frame defined by 1050 scanning lines, which are twice as large as the scanning lines in the standard television system, has been developed especially in the field of medical image instruments in order to improve diagnostic capability based on medical images. Under the situations, the digital VTR whose ability to record and reproduce images is limited to images pursuant to the standard television system can not be employed for recording and reproducing the medical images of high-definition. In some applications, a digital VTR has been proposed which can record and reproduce the image frame defined by 1050 scanning lines but this type of digital VTR is increased in size and cost and is therefore impractical.